Process for the production of tires of
small dimensions



United States Patent 3,211,819 PROCESS FOR THE PRODUCTION OF TIRES OF SMALL DIMENSIONS Raymond Guyot, Paris, France, assignor to Textiie &

Chemical Research Company (Vaduz) Limited, a corporation of Liechtenstein No Drawing. Filed Mar. 26, 1963, Ser. No. 267,915 Claims priority, application France, Mar. 29, 1962, 892,693 1 Ciaim. (Cl. 264326) This invention relates to the production of pneumatic tires, and relates more particularly to the preparation of pneumatic tires of small dimensions reinforced by cabled yarns of synthetic materials.

Cabled yarns consisting of synthetic textile materials, notably those based on polyamides such as polyhexamethylene adipamide, are being employed on an increasing scale in the reinforcement of pneumatic tires. In the case of tires of large calibre, it has proved necessary to subject the prevulcanized articles to an expansion in order to compensate for the shrinkage which cabled yarns consisting of synthetic textile fibres undergo at the vulcanization temperature.

However, expansion is impractical in the case of tires for bicycles for reasons of cost. In small-size tires for this application, cabled yarns of synthetic textile fibres have interesting advantages such as high tensile strength, low sensitivity to water and impact resistance. '1

The manufacture of small-size pneumatic tires Without expansion has given rise to serious disadvantages, of which the two main ones are:

(1) The cabled yarns tend to protrude into the interior of the tires.

(2) The tires are often greatly deformed and twisted.

These two defects are due to the shrinkage of cabled yarns at the vulcanization temperature.

According to the present invention, these defects can be obviated and pneumatic tires reinforced with cabled yarns consisting of synthetic textile materials having entirely satisfactory appearance and properties can be produced without the aid of expansion after the prevulcanization by use of rubber preparations having a high rate of vulcanization, the rubber which envelopes the cabled yarns of synthetic textile fibres having to reach a sufficient consistency before the cabled yarns can contract due to thermal action.

For cabled yarns consisting of polyhexamethylene adipamide, use is made more especially of preparations which have a vulcanization rate corresponding to 3 minutes or less, measured on the Wallace vulcanometer, at a vulcanization temperature of 140 C.

The invention is illustrated by the following example of an embodiment, but it is to be understood that this example has no limiting character and that the invention also includes any variant in the same spirit.

3,211,819 Patented Oct. 12, 1965 Example Natural rubber 110 Synthetic rubber SBR Carbon black 55 Inert mineral filler Mineral oil 8.5 Diphenylguanidine 0.9 Mercaptobenzothiazole 1.6 Zinc oxide 8.5 Sulphur 4 The calendered sheet is molded and it is vulcanized for 3 minutes at 185 C. The tires removed from the mold are free from the aforesaid defects and have entirely satisfactory appearance and properties.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention.

What is hereby claimed and desired to be secured by Letters Patent is:

The process for the production of small size tires for bicycles which are reinforced by nylon tire cords, capable of undergoing shrinkage under the action of heat as used during vulcanization, which comprises embedding said nylon tire cord reinforcement in a rubber mix which is capable of being vulcanized in three minutes at a temperature of C. molding and vulcanizing said mix at said temperature under conditions to produce a tire wherein the nylon cords have not been appreciably shrunken.

References Cited by the Examiner UNITED STATES PATENTS 2,623,024 12/52 Barton 260-5 2,679,088 5/54 Mehergetal 152359 FOREIGN PATENTS 1/48 Great Britain.

OTHER REFERENCES Introduction To Rubber Technology, edited by Maurice 0 Morton, copyright 1959, pages 100 and 101 relied upon.

ARTHUR L. LA POINT, Primary Examiner. 

